The use of wireless communications for in-home, in-building networks, and/or direct communication is increasing in popularity and spawning relatively new standards including, but not limited to, Bluetooth, IEEE 802.11a, IEEE 802.11b, et cetera. As is known for wireless communications, data is modulated onto at least one radio frequency (RF) carrier frequency and transmitted as an RF modulated signal by a radio transmitter. A radio receiver receives the RF modulated signal and demodulates it to recapture the data.
As is further known, there are a variety of modulation/demodulation protocols that may be used for wireless communications. Such modulation/demodulation protocols include amplitude modulation (AM), frequency modulation (FM), amplitude shift-keying (ASK), frequency shift-keying (FSK), phase shift-keying (PSK), orthogonal frequency division multiplexing (OFDM), and/or variations thereof.
Regardless of the particular modulation/demodulation protocol, a radio receiver generally includes an antenna section, a filtering section, a low noise amplifier, an intermediate frequency (IF) stage and a demodulator. In operation, the antenna section receives RF modulated signals and provides them to the filtering section, which passes RF signals of interest to the low noise amplifier. The low noise amplifier amplifies the received RF signals and provides the amplified PF signals of interest to the IF stage. The IF stage includes one or more local oscillators, one or more mixers, and one or more adders to step-down the frequency of the RF signals to an intermediate frequency or base band frequency. The IF stage provides the IF or base-band signals to the demodulator, which, based on the particular modulation/demodulation protocol, recaptures the data.
While the basic elements of a radio receiver operating in accordance with one wireless standard perform generally the same functions as the basic elements of a radio receiver operating in accordance with another wireless standard, the specific functionality and construct of such elements may vastly differ. For example, the elements of a radio receiver designed in accordance with the Bluetooth specification have a substantially different specific functionality, and thus construct, than corresponding elements of a radio receiver designed in accordance with the IEEE 802.11b standard.
The specific functionality differences between the basic elements of a Bluetooth radio receiver and those of an IEEE 802.11b radio receiver result from the differences between the physical layer requirements of the two specifications. For instance, Bluetooth provides up to a 1 megabit-per-second data rate by employing a frequency-hopping scheme (i.e., 97 hops at 1 megahertz spacing) in the 2.4 GHz frequency band, such that the frequencies of interest are 2.402 GHz to 2.480 GHz. Bluetooth also specifies an FSK modulation/demodulation scheme and provides for 3 power classes (e.g., 1 mW, 2.5 mW and 100 mW). As such, a Bluetooth radio receiver includes a low noise amplifier, a 1st IF stage operating with a 2 MHz intermediate frequency, band-pass filters, a 2nd IF stage operating with a base-band frequency, and an FSK demodulator.
The IEEE 802.11b standard provides a variable data rate of 1, 2, 5.5, or 11 Mbps (megabits-per-second) by employing a direct sequence spread spectrum (DSSS) transmission scheme in the 2.4 GHz frequency band, such that the frequencies of interest are 2.400 GHz to 2.483 GHz. To achieve the 11 Mbps data rate, data is encoded using an 8-bit complimentary code keying (CCK) algorithm and modulated using a differential quadrature phase shift-keying (DQPSK) scheme. For a 5.5 megabit-per-second operation, the CCK encoded data is modulated using a differential binary phase shift-keying (DBPSK) modulation scheme. As such, an IEEE 802.11b compliant radio receiver includes a low noise amplifier, an IF stage having a baseband intermediate frequency, low pass filters, gain stages, and a DQPSK and/or DBPSK demodulator.
Since both IEEE 802.11b and Bluetooth specifications were created for localized (e.g., in-building, in-home, in parking lots, in stadiums, in hospitals, et cetera) wireless communications, it is conceivable that some wireless applications would be better served by Bluetooth while other wireless applications would be better served by 802.11b. In such an instance, it would be desirable for a wireless communication device to be able to operate in accordance with both the Bluetooth standard and the 802.11b standard. But, to do so, the device requires a separate Bluetooth radio (i.e., Bluetooth radio transmitter and Bluetooth radio receiver) and a separate 802.11b radio (i.e., 802.11b radio transmitter and 802.11b radio receiver). Such additional circuitry, while providing additional functionality, adds to the cost and complexity of such wireless devices.
Therefore, a need exists for an integrated radio receiver and/or integrated radio transmitter that support multiple wireless communication standards including, but not limited to Bluetooth and IEEE 802.11b.